To prevent leakage of body exudates from absorbent articles such as feminine care pads or napkins and disposable diapers, it is desirable that the exudates not reach the edges of the absorbent material in the article. A xe2x80x9ccenter fillxe2x80x9d strategy is desirable for leakage control, wherein fluids are preferentially held in a central region of the article. Unfortunately, in traditional absorbent articles, there is generally no barrier to bulk flow or capillary wicking from the target region to the edges of the article, so leaking from the edges of the article is a persistent problem. Thus, in traditional articles, fluid entering the center of the article still has the potential to travel to the sides and leak. Flow from the center to the sides can be especially rapid when the article is compressed, bringing the wet central portion of the article in contact with absorbent material at the sides of the article.
A variety of wicking barriers have been proposed, including barriers between absorbent components of an absorbent core. However, such wicking barriers generally serve a negative purpose only, that of hindering wicking and lack means for directly channeling flow. What is needed are flow barriers in an absorbent article that not only obstruct flow but provide void volume for receiving flow and means for directing flow to available absorbent material. Ideally, such barriers should also promote effective center fill performance of the absorbent article and efficient use of the absorbent materials of the absorbent core, while also functioning to improve body fit.
In an absorbent article comprising a central absorbent member separated from the rest of the absorbent core by a flexible wicking barrier such as a polymeric film that hinders flow from the central absorbent member to the longitudinal sides of the article, it has been discovered that the wicking barrier can be modified to define cuffs that intercept and receive fluid. The cuffs can extend longitudinally or in other directions to form flow channels capable of directing fluid to desired destinations in the absorbent core. These benefits can be achieved when the wicking barrier reverses direction (e.g., is folded back upon itself) with opposing edges of the wicking barrier being closer to each other than are the outer portions of the wicking barrier where the reversal or folding occurs.
Desirably, the cuffs extend in a substantially longitudinal direction with the loci of folding occurring in the longitudinal direction, with the longitudinal edges of the wicking barrier reversing back toward the longitudinal centerline of the article. Thus, a transverse cross-section of an absorbent article with substantially longitudinal wicking barrier cuffs can show that the wicking barrier extends laterally outward from the sides of the central absorbent member toward the longitudinal sides of article but then reverses direction such that the edges of the wicking barrier are disposed laterally inward from the laterally outermost portions of the wicking barrier. Spacer means can also be provided to hold the cuff open, providing void space between the upper and lower portions of the folded-over wicking barrier, with the void space being accessible to fluid flowing from the center of the absorbent article toward the longitudinal sides thereof.
Hence, in one aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a target zone and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) an absorbent core positioned between the topsheet and the backsheet, the absorbent core comprising an outer absorbent member and a central absorbent member, the outer absorbent member having a width in the target zone greater than the width of the central absorbent member in the target zone; and
d) a wicking barrier spanning a vertical distance between the outer absorbent member and the central absorbent member, further comprising a folded-over portion above the absorbent core forming a wicking barrier cuff open toward the central absorbent member, the wicking barrier cuff further comprising optional spacer means to hold the cuff open to receive fluid.
In another aspect, the invention resides in an absorbent article having a longitudinal direction, a transverse direction, a vertical direction substantially normal to both the longitudinal and transverse directions, and a body side, comprising:
a) a fluid pervious topsheet on the body side of the article;
b) a backsheet connected to the topsheet;
c) an absorbent core having a body side surface, the core being disposed between the backsheet and the topsheet, the core comprising an outer absorbent member having a central void open toward the body side of the article, and a central absorbent member disposed over the central void of the outer absorbent member and extending into the void; and
d) a wicking barrier disposed between the outer absorbent member and the central absorbent member, the wicking barrier comprising a vertical component between the outer absorbent member and the central absorbent member and a wicking barrier cuff on the body side surface of the absorbent core.
The central void can be a hole that passes completely through the outer absorbent member, or can be a depressed region within a contiguous, uninterrupted outer absorbent member. In one embodiment, the central void longitudinally divides the outer absorbent member into two discontiguous sections. In other embodiments, the outer absorbent member is divided by the central void in the crotch region, but the outer absorbent member may be contiguous in the front or back portions of the article (i.e., the central void does not extend substantially beyond the crotch region).
In another aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a target zone and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) an absorbent core positioned between the topsheet and the backsheet, the absorbent core comprising a central portion and an outer portion; and
d) a wicking barrier spanning a vertical distance between the outer portion and the central portion, further extending laterally outward from the central portion toward a longitudinal side of the article to span a first horizontal distance, whereupon the wicking barrier folds back upon itself toward the longitudinal centerline, spanning a second horizontal distance and forming a wicking barrier cuff with an upper layer and a lower layer, the cuff being open toward the central absorbent member and closed toward the longitudinal sides of the article.
In another aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a longitudinal centerline, a target zone and a body side, the absorbent article comprising:
a) a backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) a central absorbent member positioned between the topsheet and the backsheet, the central absorbent member comprising longitudinal sides and a body-side surface;
d) a wicking barrier that extends beneath the central absorbent member, wraps the longitudinal sides thereof, and thereupon extends a horizontal distance on the body-side surface thereof toward the longitudinal centerline of the absorbent article; and
e) spacer means to provide void space between the central absorbent member and the portion of the wicking barrier above the body-side surface of the central absorbent member, thereby forming a wicking barrier cuff.
In another aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a target zone, a body side, and a longitudinal centerline, the absorbent article comprising:
a) a backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) an absorbent core positioned between the topsheet and the backsheet, the absorbent core comprising longitudinal sides, a body-side surface, a lower absorbent layer having a width, and an upper absorbent layer having a width substantially less than the width of the lower absorbent layer; and
d) a substantially impervious wicking barrier extending along a portion of the body-side surface of the lower absorbent layer in the target region and further being folded about a substantially longitudinal folding line toward the longitudinal centerline of the absorbent article to form a wicking barrier cuff having an upper layer and a lower layer, the upper layer being attached to the topsheet, and the folding line being transversely away from the upper absorbent layer.
In this embodiment, the folding line is transversely away from the upper absorbent layer because there is a finite distance in the transverse direction, normal to the longitudinal direction, such as at least 0.5 mm or about 2 mm, between the folding line and the nearest longitudinal side of the upper absorbent layer. The upper layer of the wicking barrier can contact the body-side surface of the upper absorbent layer of the absorbent core, a geometrical configuration which helps to hold the wicking barrier cuff open to receive fluid. Generally, lateral compression in the target region will cause the portion of the topsheet attached to the upper layer of the wicking barrier cuff to deflect upwards, forming a dynamic bubble cuff capable of receiving fluid flowing transversely outward from the center of the article.
In still another aspect, the invention resides in a method for producing an absorbent article having a longitudinal centerline, the method comprising:
a) preparing a lower layer of absorbent material having a width;
b) disposing a wicking barrier over the lower layer of absorbent material, the wicking barrier having a width substantially greater than the width of the lower layer of absorbent material;
c) disposing an upper absorbent layer over the wicking barrier, the upper absorbent layer having a width less than the width of the outer absorbent member;
d) folding the transversely outer portions of the wicking barrier back toward the longitudinal centerline of the article to form wicking barrier cuffs each comprising a lower layer and an upper layer, the upper layer having a free end toward the longitudinal centerline of the article;
e) disposing a backsheet beneath the lower layer of absorbent material; and
f) disposing a topsheet over the article and attaching the topsheet to the backsheet.
The lower absorbent layer may further comprise a central void or depression into which the upper absorbent layer or an absorbent pledget will fit.
In yet another aspect, the invention resides in a method for producing an absorbent article having a central absorbent member, a garment side, a body side, and a longitudinal centerline, the method comprising:
a) providing a central strip of absorbent material and two side strips of absorbent material to form an incipient absorbent core;
b) placing a thin, flexible wicking barrier below the central strip and above the two side strips, the wicking barrier having a width substantial greater than the width of the central strip;
c) upwardly folding the transversely outer portions of the wicking barrier back upon themselves and toward the longitudinal centerline of the central strip to form wicking barrier cuffs;
d) disposing a backsheet beneath the central strip and two side strips, the backsheet having larger in-plane dimensions that the combined central strip and two side strips; and
e) disposing a topsheet over the central absorbent strip and two side strips, wherein the topsheet is further connected to the backsheet at the outer periphery thereof.
The above method may further comprise inserting or providing spacer means in the wicking barrier cuff and/or adhesively attaching the topsheet to the body-side surface (i.e., the upper layer) of the wicking barrier cuffs.
Generally, absorbent articles according to the present invention comprise a topsheet attached to a backsheet with an absorbent core and a wicking barrier therebetween. The absorbent core comprises a central absorbent member that is desirably surrounded by a wider outer absorbent member, with a wicking barrier disposed along at least a portion of the sides of the central absorbent member to hinder fluid flow from the central absorbent member to the sides of the article. The topsheet is liquid pervious to permit intake of fluid and can be any material known in the art such as a spunbond web or apertured film. The backsheet is generally liquid impervious and can be a polyolefin film, for example. The central absorbent member and outer absorbent member or other absorbent components can comprise any known absorbent material known to be useful in absorbent articles, such as cellulosic airlaid webs, fluff pulp, tissue layers, coform, peat moss, and the like. In those embodiments of the present invention having a separate outer absorbent member and a central absorbent member with a wicking barrier therebetween, the central absorbent member generally is the primary absorbent component of the article. The outer absorbent member typically serves as a frame or shaping element for the absorbent article, in part by virtue of its ability to remain dry and resilient in use, but also offers additional absorbent capacity for fluid retention. The outer absorbent member is generally wider and also can be longer than the central absorbent member, and preferably has a central void for receiving at least a portion of the central absorbent member. Alternatively, the outer absorbent member can be a lower layer wider than a narrower upper layer serving as the central absorbent member, with the wicking barrier separating the upper layer from the lower layer and forming at least one and preferably two cuffs to intercept fluid escaping from the upper layer.
The wicking barrier can be any thin, flexible material capable of preventing or hindering flow away from the central absorbent member, with impervious polymeric films such as polyethylene or polypropylene being especially preferred. In a preferred embodiment, the wicking barrier spans a vertical distance between the central absorbent member and an outer absorbent member, and further spans a horizontal distance above the body-side surface of the outer absorbent member. The cuffs formed from a folded portion of the wicking barrier above the absorbent core not only help prevent fluid from reaching the longitudinal sides of the absorbent article, but also can help channel fluid to underutilized portions of the absorbent core for improved absorption. Due to the horizontal component on the surface of the absorbent core, the wicking barrier also serves to prevent fluid communication between the central absorbent member and the outer absorbent member when the article is laterally compressed or bunched together in use. The wicking barrier can also help control the geometry of the absorbent article when in use under dynamic conditions, permitting flexure or folding such that the central region of the core (e.g., the central absorbent member where applicable) is deflected toward the body.
Spacer means to hold the wicking barrier cuffs open can include any of the following or combinations thereof or their equivalents:
1. Attachment of an upper portion of the folded wicking barrier to a structure at a substantially higher elevation than the lower portion of the folded wicking barrier. For example, an upper portion of the wicking barrier may be attached to an elevated central absorbent member which rises above the plane of the outer absorbent member, or may be attached to a portion of the topsheet which in turn is held above the plane of the outer absorbent member by virtue of an elevated central absorbent member.
2. Spacers of absorbent material or non-absorbent material to keep the two layers of barrier material apart. The use of materials which expand in the z-direction when wet can be especially useful for good performance of the article in use.
3. Corrugations, wrinkles, embossments, ribs, or other three-dimensional elements in or on the wicking barrier. For example, thermal embossing of the longitudinal sides of the wicking barrier can yield a sinusoidal or corrugated effect along the edges, similar to the edges of a scallop shell, resulting in open voids directed toward the longitudinal centerline of the absorbent article. The scalloped voids permit fluid flow into the cuff.
A wicking barrier with a scalloped, three-dimensional edge provides elevated portions of the wicking barrier edge lying above the absorbent core and providing void volume for intercepting lateral flow of fluid along the surface of the absorbent core. Similar effects can be achieved with other spacer means described above.
Particularly beneficial improvements in leakage control can be achieved through the interaction between the topsheet and the folded-over portion of the wicking barrier on the surface of the absorbent core, wherein lateral compression of the absorbent article causes a loop or xe2x80x9cbubblexe2x80x9d of topsheet material to rise along the sides of the article, the loop running substantially in the longitudinal direction, thus helping to provide a xe2x80x9cdynamic bubble cuffxe2x80x9d that is not present until the article is worn. The dynamic bubble cuff feature is not normally seen in other absorbent articles where the topsheet, such as a nonwoven web, may be adhesively attached over its entire surface to the underlying absorbent core and backsheet. In the present invention, adhesive material joining the topsheet to the upper layer of the folded-over portion of a wicking barrier on the surface of the absorbent core does not directly connect the topsheet to the absorbent core, but connects it to a layer of the wicking barrier that can rise vertically away from the absorbent core. In fact, the upper layer of the folded-over portion of the wicking barrier can move and flex relative to the absorbent core with little resistance from friction, apart from its connection to the lower layer of the folded-over portion along a folding line, provided that any active adhesive on the wicking barrier in the folded-over portion is on the side that contacts the topsheet. The inner surfaces of the wicking barrier which can contact each other should be substantially free of adhesive to prevent the two layer from becoming sealed. Thus, in the present invention, an article may lie flat with little or no indication of a three-dimensional cuff rising vertically away from the plane of the topsheet, but when the article undergoes lateral compression, a bubble with a substantially longitudinal orientation rises away from the absorbent core to act as a barrier for leakage along the surface of the absorbent article and as a means for intercepting and redirecting flow. The bubble, or dynamic bubble cuff, comprises the upper layer of the folded-over portion of the wicking barrier and the portion of the topsheet attached thereto. A dynamic bubble cuff is particularly likely to form when the absorbent core comprises a separate outer absorbent member separated from a central absorbent member by the wicking barrier, as described in pending application Ser. No. 09/165,875, xe2x80x9cAbsorbent Article with Center Fill Performance,xe2x80x9d filed Oct. 2, 1998, herein incorporated by reference.
The absorbent core may further comprise a central rising member under the central absorbent member or under or within the absorbent core to translate lateral compression of the core into vertical rising of the central portion of the core for improved body fit. Central rising members and related embodiments are described in commonly owned copending application xe2x80x9cCenter-fill Absorbent Article with Central Rising Memberxe2x80x9d by Chen et al., Ser. No. 094/1259, now U.S. Pat. No. 6,492,574 filed the same day as the present application.
Possible uses of the present invention include absorbent articles for intake, distribution, and retention of human body fluids. Likewise, the present invention can be applied to diapers, disposable training pants, other disposable garments such as incontinence pads, bed pads, medical absorbents and wound dressings. The articles of the present invention provide significant leakage protection, fluid center-fill absorptive performance, and other desirable attributes for absorbent articles.
xe2x80x9cAbsorbency Under Loadxe2x80x9d (AUL) is a measure of the liquid retention capacity of a material under a mechanical load. It is determined by a test which measures the amount in grams of an aqueous solution, containing 0.9 weight percent sodium chloride, a gram of a material can absorb in 1 hour under an applied load or restraining force of about 2 kPa (0.3 pound per square inch).
The AUL apparatus comprises a Demand Absorbency Tester (DAT) as described in U.S. Pat. No. 5,147,343, issued Sep. 15, 1992 to Kellenberger, herein incorporated by reference, which is similar to a GATS (Gravimetric Absorbency Test System), available from M/K Systems, Danners, Mass.
As used herein, a material is said to be xe2x80x9cabsorbentxe2x80x9d if it can retain an amount of water equal to at least 100% of its dry weight as measured by the test for Intrinsic Absorbent Capacity given below (i.e., the material has an Intrinsic Absorbent Capacity of at about 1 or greater). Desirably, the absorbent materials used in the absorbent members of the present invention have an Intrinsic Absorbent Capacity of about 2 or greater, more specifically about 4 or greater, more specifically still about 7 or greater, and more specifically still about 10 or greater, with exemplary ranges of from about 3 to about 30 or from about 4 to about 25 or from about 12 to about 40.
As used herein, xe2x80x9cabsorbent capacityxe2x80x9d refers to the total mass of water that a specified quantity of absorbent material can hold, and is simply the Intrinsic Absorbent Capacity multiplied by the dry mass of the absorbent material. Thus 10 g of material having an Intrinsic Absorbent Capacity of 5 has an absorbent capacity of 50 g (or about 50 ml of fluid).
As used herein, xe2x80x9cbulkxe2x80x9d and xe2x80x9cdensity,xe2x80x9d unless otherwise specified, are based on an oven-dry mass of a sample and a thickness measurement made at a load of 0.34 kPa (0.05 psi) with a 7.62-cm (three-inch) diameter circular platen. Thickness measurements of samples are made in a TAPPI-conditioned room (50% relative humidity and 23xc2x0 C.) after conditioning for at least four hours. Samples should be essentially flat and uniform under the area of the contacting platen. Bulk is expressed as volume per mass of fiber in cc/g and density is the inverse, g/cc.
As used herein, the term xe2x80x9ccellulosicxe2x80x9d is meant to include any material having cellulose as a major constituent, and specifically comprising at least 50 percent by weight cellulose or a cellulose derivative. Thus, the term includes cotton, typical wood pulps, nonwoody cellulosic fibers, cellulose acetate, cellulose triacetate, rayon, thermomechanical wood pulp, chemical wood pulp, debonded chemical wood pulp, milkweed, or bacterial cellulose.
As used herein, xe2x80x9cCentral Elevationxe2x80x9d is defined as the height difference between the center of the central absorbent member along the transverse centerline of the article and the average height of the longitudinal sides of the central absorbent member along the transverse centerline of the article at the end of the Vertical Deformation Test hereinafter described. The Central Elevation for absorbent articles of the present invention can be at least about 0.5 cm, specifically at least about 1 cm, and more specifically at least about 1.2 cm and up to about 10 cm, Desirably, an absorbent article of the present invention exhibits an increase in Central Elevation in the crotch region of at least about 20%, and more specifically at least about 50%, relative to the Central Elevation in the crotch region exhibited by an essentially identical absorbent article without a shaping line.
As used herein, the xe2x80x9ccrotch regionxe2x80x9d of an absorbent article refers to the generally central region that will be in contact with the crotch of the user, near the lowermost part of the torso, and resides between the front and rear portions of the article. Typically the crotch region contains the transverse centerline of the article and generally spans approximately 7 to 10 cm in the longitudinal direction.
Many articles of the present invention are intended to be worn in the crotch of a wearer, and thus have crotch regions. However, the present invention can also be applied to other articles such as underarm pads or wound dressings where a crotch region may not exist. In such cases, the article will have a region where fluid intake is intended to occur, termed the xe2x80x9ctarget region.xe2x80x9d The portion of the article including the longitudinal length of the target region and the full transverse width of the article normal to length of the target region is defined herein as the xe2x80x9ctarget zone.xe2x80x9d For articles intended to be worn in the crotch, the terms xe2x80x9ctarget zonexe2x80x9d and xe2x80x9ccrotch regionxe2x80x9d are generally synonymous, whereas xe2x80x9ctarget regionxe2x80x9d generally excludes the portions of the absorbent core near the longitudinal sides since the intended area for fluid intake is generally substantially central in the absorbent article.
As used herein, the term xe2x80x9cextensiblexe2x80x9d refers to articles that can increase in at least one of their dimensions in the x-y plane by at least 10% and desirably at least 20%. The x-y plane is a plane generally parallel to the faces of the article. The term extensible includes articles that are stretchable and elastically stretchable (defined below). In the case of a sanitary napkin comprising an absorbent core, for example, the article and the absorbent core are desirably extensible both in length and width. The absorbent article, however, may only be extensible in one of these directions. Preferably, the article is extensible at least in the longitudinal direction. Examples of extensible materials and articles, and their methods of preparation, are disclosed in U.S. Pat. No. 5,611,790, issued Mar. 18, 1997 to Osborn, herein incorporated by reference in its entirety.
As used herein, the term xe2x80x9cflexure-resistantxe2x80x9d refers to an element which will support a bending moment, in contrast to an element which will support only axial forces. Likewise, as used herein, xe2x80x9cflexure resistancexe2x80x9d is a means of expressing the flexibility of a material or article and is measured according to the Circular Bend Procedure described in detail in U.S. Pat. No. 5,624,423, issued Apr. 29, 1997 to Anjur et al., herein incorporated by reference in its entirety. Flexure resistance is actually a measurement of peak bending stiffness modeled after the ASTM D4032-82 Circular Bend Procedure. The Circular Bend Procedure of Anjur et al. is a simultaneous multidirectional deformation of a material in which one face of a specimen becomes concave and the other face becomes convex. The Circular Bend Procedure gives a force value related to flexure-resistance, simultaneously averaging stiffness in all directions. For comfort, the absorbent article desirably has a flexure-resistance of less than or equal to about 1,500 grams, more specifically about 1000 grams or less, more specifically still about 700 grams or less and most specifically about 600 grams or less. For shaping performance, the central absorbent member as well as the outer absorbent member can have a flexure resistance of at least about 30 grams, more specifically at least about 50 grams, and most specifically at least about 150 grams.
As used herein, xe2x80x9cFree Swell Capacityxe2x80x9d (FS) is the result of a test which measures the amount in grams of an aqueous solution, containing 0.9 weight percent sodium chloride, that a gram of a material can absorb in 1 hour under negligible applied load. The test is done as described above for the AUL test, except that the 100 gm weight used in the AUL test is not placed on the sample.
The Free Swell Capacity of the materials of the present invention can be above 8, more specifically above 10, more specifically above 20, and most specifically above 30 grams/gram.
As used herein, xe2x80x9cFree Swell:AUL Ratioxe2x80x9d is the ratio of Free Swell Capacity to AUL. It will generally be greater than one. The higher the value, the more sensitive the material is to compressive load, meaning that the sample is less able to maintain its potential pore volume and capillary suction potential under load. Desirably, the materials of the present invention have xe2x80x9cFree Swell:AUL Ratioxe2x80x9d of about 4 or less, more specifically about 2 or less, more specifically still about 1.5 or less, and more specifically about 1.3 or less, with an exemplary range of from about 1.2 to about 2.5.
As used herein, xe2x80x9chigh yield pulp fibersxe2x80x9d are those papermaking fibers of pulps produced by pulping processes providing a yield of about 65 percent or greater, more specifically about 75 percent or greater, and still more specifically from about 75 to about 95 percent. Yield is the resulting amount of processed fiber expressed as a percentage of the initial wood mass. High yield pulps include bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP), pressure/pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high yield sulfite pulps, and high yield Kraft pulps, all of which contain fibers having high levels of lignin.
As used herein, the term xe2x80x9chorizontal,xe2x80x9d refers to directions in the plane of the article that are substantially parallel to the body-side surface of the article, or, equivalently, substantially normal to the vertical direction of the article, and comprises the transverse direction and the longitudinal direction of the article, as well as intermediate directions. The orientation of components in an article, unless otherwise specified, is determined as the article lies substantially flat on a horizontal surface.
As used herein, the term xe2x80x9chydrophobicxe2x80x9d refers to a material having a contact angle of water in air of at least 90 degrees. In contrast, as used herein, the term xe2x80x9chydrophilicxe2x80x9d refers to a material having a contact angle of water in air of less than 90 degrees.
As used herein, xe2x80x9cIntrinsic Absorbent Capacityxe2x80x9d refers to the amount of water that a saturated sample can hold relative to the dry weight of the sample and is reported as a dimensionless number (mass divided by mass). The test is performed according to Federal Government Specification UU-T-595b. It is made by cutting a 10.16 cm long by 10.16 cm wide (4 inch long by 4 inch wide) test sample, weighing it, and then saturating it with water for three minutes by soaking. The sample is then removed from the water and hung by one corner for 30 seconds to allow excess water to be drained off. The sample is then re-weighed, and the difference between the wet and dry weights is the water pickup of the sample expressed in grams per 10.16 cm long by 10.16 cm wide sample. The Intrinsic Absorbent Capacity value is obtained by dividing the total water pick-up by the dry weight of the sample. If the material lacks adequate integrity when wet to perform the test without sample disintegration, the test method may be modified to provide improved integrity to the sample without substantially modifying its absorbent properties. Specifically, the material may be reinforced with up to 6 lines of hot melt adhesive having a diameter of about 1 mm applied to the outer surface of the article to encircle the material with a water-resistant band. The hot melt should be applied to avoid penetration of the adhesive into the body of the material being tested. The corner on which the sample is hung in particular should be reinforced with external hot melt adhesive to increase integrity if the untreated sample cannot be hung for 30 seconds when wet.
xe2x80x9cPapermaking fibers,xe2x80x9d as used herein, include all known cellulosic fibers or fiber mixes comprising cellulosic fibers. Fibers suitable for making the webs of this invention comprise any natural or synthetic cellulosic fibers including, but not limited to nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and woody fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, and aspen. Woody fibers can be prepared in high-yield or low-yield forms and can be pulped in any known method, including kraft, sulfite, high-yield pulping methods, and other known pulping methods. Chemically treated natural cellulosic fibers can be used such as mercerized pulps, chemically stiffened or crosslinked fibers, or sulfonated fibers. Suitable papermaking fibers can also include recycled fibers, virgin fibers, or mixes thereof.
As used herein, a xe2x80x9cpledgetxe2x80x9d refers to an absorbent insert within an absorbent core having at least one of a width and a length smaller than the respective width and length of the absorbent core. A pledget is generally used to cause deformation or shaping of an adjoining layer of an absorbent article, and in the present invention, can be of use in shaping a pad or creating a medial hump in the pad for improved fit against the body of the wearer.
The term xe2x80x9csanitary napkinxe2x80x9d, as used herein, refers to an article which is worn by females adjacent to the pudendal region that is intended to absorb and contain the various exudates which are discharged from the body (e.g., blood, menses, and urine). While the present invention is shown and described in the form of a sanitary napkin, it should be understood that the present invention is also applicable to other feminine hygiene or catamenial pads such as panty liners, or other absorbent articles such as diapers or incontinence pads. The term xe2x80x9cfeminine care padxe2x80x9d as used herein is synonymous with sanitary napkin.
The term xe2x80x9cstretchablexe2x80x9d, as used herein, refers to articles that are extensible when stretching forces are applied to the article and offer some resistance to stretching. The terms xe2x80x9celastically stretchablexe2x80x9d or xe2x80x9celastically extensiblexe2x80x9d are intended to be synonymous. These terms, as used herein, mean that when in-plane stretching forces are removed, the article or absorbent fibrous structure will tend to return toward its unextended or unstretched dimensions (or original dimensions). It need not return all the way to its unstretched dimensions, however. It may return to relaxed dimensions between its unstretched dimensions and extended (or stretched dimensions).
As used herein, xe2x80x9cthicknessxe2x80x9d of a fluff pad or other absorbent element refers to thickness measured with a platen-based thickness gauge having a diameter of 7.62 cm at a load of about 0.05 pounds per square inch (psi) [about 35 kilograms per square meter]. The thickness of the central absorbent member or the outer absorbent member or of the absorbent article in general can be from about 2 mm to about 50 mm, more specifically from about 3 mm to about 25 mm, more specifically still from about 3 mm to about 15 mm, and most specifically from about 4 mm to about 10 mm. Ultrathin articles can have a thickness less than about 6 mm.
As used herein, the term xe2x80x9ctransversexe2x80x9d refers to a line, axis, or direction which lies within the plane of the absorbent article and is generally perpendicular to the longitudinal direction. The z-direction is generally orthogonal to both the longitudinal and transverse centerlines. The term xe2x80x9clateralxe2x80x9d refers to substantially in-plane directions having a predominately transverse component. Likewise, xe2x80x9cinwardly lateral compressionxe2x80x9d refers to compression directed from the longitudinal sides of an article toward the longitudinal centerline thereof, applied substantially in the transverse direction.
The degree of elevation of the central absorbent member can be quantified in terms of a Vertical Deformation test. As used herein, xe2x80x9cVertical Deformationxe2x80x9d refers to the height increase experienced by the body-side surface of an absorbent article when the longitudinal sides in the crotch reason are gripped and steadily moved inward toward the longitudinal axis of the article, decreasing the span between the longitudinal sides by 1.5 cm. The Vertical Deformation test apparatus comprises two clamps having a clamp width (longitudinal length of the clamped portion of the edge of the article) of 5 cm. One clamp is stationary and the other is on a track that permits the clamp to slide to increase or decrease the distance between the clamps while keeping the clamp aligned and parallel to the other clamp. The clamps should be tilted downward at an angle of 20 degrees relative to horizontal, such that both outer edges of the absorbent article are slightly elevated relative to the nearest crease line, thus somewhat simulating the positioning of the outward edges of the absorbent article that may be induced by panties with elevated elastic edges in the crotch region. The clamps are 5 cm above the surface of the track, permitting a pad to be suspended in air between the clamps, gripped in the crotch area such that a portion of the longitudinal sides of the absorbent core are held, with the clamps extending inward no more than about 3 mm from the outer edge of the absorbent core. The article should be held substantially taut in the region between the clamps without damaging the article, such that the crotch region is substantially horizontal before lateral compression begins. At a rate of about 0.5 centimeters per second (cm/s), the slidable clamp is moved smoothly toward the fixed clamp by a distance of 50% of the initial width of the article in the crotch region (or less if the article become incompressible such that more than about 5 kg of force is required to further compress the article). The height of the center of the pad or absorbent article is recorded before the clamp is moved and after the clamp is moved, yielding a difference that is reported as the Vertical Deformation. An increase in height is reported as a positive number, while a decrease is reported as a negative number. Desirably, the Vertical Deformation of the absorbent article is at least about 0.5 cm. Specifically, the Vertical Deformation is at least about 1 cm, and more specifically is at least about 1.5 cm and up to about 10 cm. Desirably, an absorbent article of the present invention exhibits an increase in Vertical Deformation in the crotch region of at least about 20%, and more specifically at least about 50%, relative to the Vertical Deformation in the crotch region exhibited by an essentially identical absorbent article without a shaping line.
As used herein, xe2x80x9cWet Bulkxe2x80x9d is based on a caliper measurement of a sample according to the definition of xe2x80x9cbulkxe2x80x9d above (at 0.344 kPa), except that the conditioned sample is uniformly misted with deionized water until the moistened mass of the sample is approximately 250% of the dry mass of the sample (i.e., the added mass of the moisture is 150% of the dry sample weight). If the sample cannot absorb and retain enough moisture from misting to increase the mass by 150%, then the highest level of achievable moisture add-on below 150% but still above 100% moisture add on should be used. The Wet Bulk in cc/g is calculated as the thickness of the substantially planar moistened sample under a load of 0.344 kPa (0.05 psi) divided by the oven-dry sample basis weight. Absorbent materials in the absorbent members of the present invention can have a Wet Bulk of about 4 cc/g or greater, more specifically about 6 cc/g or greater, more specifically still about 10 cc/g or greater, more specifically still about 10 cc/g or greater, and most specifically about 15 cc/g or greater, with an exemplary range of from about 5 cc/g to about 20 cc/g.